Process for treating tire cord fabric and improved rubber structures therefrom

ABSTRACT

The bonding of tire cord fabric to rubber is improved by treating the surface of the fabric with a solvent solution of a polyisocyanate containing a polycarbodiimide.

United States Patent [191 Bhakuni et a1. l 5

[1 1] 3,821,017 1 June 28, 1974 1 PROCESS FOR TREATING TIRE CORD FABRIC AND IMPROVED RUBBER STRUCTURES THEREFROM [75] Inventors: Roop S. Bhakuni, Copley; John G.

Morgan, Akron, both of Ohio [73] Assignee: The Goodyear Tire & Rubber Company, Akron, Ohio [22] Filed: June 23, 1972 [21] Appl. No.: 265,875

[52] US. Cl. 117/76 T, 117/80, 117/161 KP, 117/161 P, 156/110 A, 156/315,156/331, 156/335 [51] Int. Cl B32b 25/02 [58] Field of Search 156/331, 315, 110 A, 335; 117/76 T, 80,161 KP,161P

[56] References Cited UNITED STATES PATENTS 2,990,313 6/1961 Knowles et a1. 156/110 A Primary Examiner-Ralph Husaclk Attorney, Agent, or Firm-1 W. Brunner; C.- R. Schupbach; V. G. Parker 5 7] ABSTRACT The bonding of tire cord fabric to rubber is improved by treating the surface of the fabric with a solvent solution of a polyisocyanate containing a polycarbodiimide.

10 Claims, No Drawings PROCESS FOR TREATING TIRE CORD FABRIC AND IMPROVED RUBBER STRUCTURES THEREFROM This invention relates to an improved process for treating tire cord fabric useful in the reinforcement of rubber and to improved rubber structure such as a pneumatic tire made with the fabric treated in accordance with the process of this invention.

It is known to improve the bond between the fabric and the rubber by treating the fabric with an isocyanate from a solvent solution as shown in US. Pat. No. 3,240,650. An economical process requires recycling of the solvent. Unfortunately the recycled solvent extracts finish oilsand low molecular weight fractions as well as moisture from the fabric being treated. The accumulation of moisture and finish oils in the recycled solvent is undesirable resulting in precipitates commonly referred to in the trade as dirt. When sufficient dirt accumulates in the dip tank containing the solvent and the isocyanate, the fabric being treated in the tank is undesirably affected showing up in a rubber structure such as a pneumatic tire in loss of resistance to fatigue and peel strength.

It has been discovered that these problems can be overcome by treating the tire cord fabric in a solvent solution of an isocyanate containing an effective amount of a polycarbodiimide.

The term polycarbodiimide (PCD) is meant to in clude compounds having two nitrogen atoms connected to a carbon atom by double bonds and more specifically, to compounds having the following general formula wherein R and R are radicals independently selected from the group consisting of aryl, alkyl, aralkyl or alkoxy radicals and wherein n is less than 10 and preferably between 2 and 4. The polycarbodiimides are generally substances of a highly viscous to solid nature, and depending on their molecular weight, they are substances which are more or less sparingly soluble or insoluble in organic solvents. Any suitable polycarbodiimide may be usedsuchas those obtained in accordance with. US. Pat. No. 2,941,966 whichdescribes a process of preparing polycarbodiimides using polyisocyanates in the presence of catalytic quantities of phospholines and their oxides and sulfides. The polycarbodiimides especially useful in the present invention may be shown by the following general formula wherein n islessthan l and preferably between about 4 and 2. T I

The amount of polycarbodiimide may range from about 5 percent to about 50 percent of the amount of polyisocyanate present in the solvent dip or from about 00! part to about 1.0 part and preferably from about 0.02 to about0.4 part per 100 parts of solvent.

The following isocyanates may be usedin the first treatment of the tire cordfabric when dissolvedin a suitable inert solvent for the isocyanate.

Polymethylene polyphenylisocyanate (PAPI) Triphenyl methanetriisocyanate (TMTl) 2,4-Tolylene-diisocyanate 2,4-TDI 2,6-Tolylene-diisocyanate (2,6-TDl) Bitolylene diisocyanate (TODI) Dianisidine diisocyanate (DADl) Hexamethylene diisocyanate (l-IDI) m-Phenylene diisocyanate (PDI) l-Alkyl-benzene-2,4-diisocyanate (AB-2,4-Dl) 1-Alkyl-benzene-2,5-diisocyanate (AB-2,5-DI) 2,6-Dialkyl-benzenel ,4-diisocyanate DBDI) 1-Chlorobenzene-2,4-diisocyanate (CDI) Dicyclohexylmethane-diisocyanate (CXDl) 3,3-Dimethoxy diphenyl methane-4,4-diisocyanate (DDMDI) 1-Nitrobenzene-2,4-diisocyanate (NDl) l-Alkoxy-benzene-2,4-diisocyanate (ABDI) l-Alkylbenzene-2,6-diisocyanate (ADI) m-Xylylene-diisocyanate (XDI) l ,3-Dimethyl-4,6-bis(,B isocyanatoethyl) benzenediisocyanate (DBIBDI) Hexahydrobenzidine-4,4'-diisocyanate (l-IBDI) Ethylene-diisocyanate (EDD- Propylene-1 ,3-diisocyanate (PDI) Cyclohexylene-l,2-diisocyanate (CDI) 3,3'-Dichloro-4,4-biphenylene diisocyanate (DBDl) 2,3-Dimethyl-tetramethylene diisocyanate (DTDI) p,p'-Diphenylene diisocyanate (DPDl) 2-Chlorotrimethylene diisocyanate (CTDI) Butanel ,2,2-triisocyanate (BTl 'Trimethylene diisocyanate (TMDI) Tetramethylene diisocyanate (TDI) Propylenel ,Z-diisocyanate PDl) Butylene-l ,Z-diisocyanate (BDl) Ethylidene diisocyanate (EDI) Metaphenylene diisocyanate (MPDl) Diphenylmethane 4,4'-diisocyanate (DP-4,4-Dl) Diphenyl 4,4'-diisocyanate (DPDI) l,5-Diisocyanate naphthalene (LS-DIN) 2,4-Diisocyanate chlorbenzene (2,4-DlCB) 4,4,4 "-Triisocyanate triphenyl methane (4,4',4"-

Polymethylene diisocyanate (PMDl) The amount of polyisocyanate may range from 0.l to about 2 parts and preferably from about 0.2 to about 0.5 part per l00parts of solvent.

Suitable inert solvents for the isocyanates are (l) chlorinated hydrocarbons including methylene chloride, trichlorethylene, dichlorethane, trichlorethane, (2);esters including methyl acetate, ethyl acetate, (.3) ketones including acetone and methyl ethyl ketone, and (4) aromatic solvents including benzene and toluene. These solvents are removed from the cord by heating the cord at about the boiling point of the solvent and usually between about F. to about 350 F.

This invention is described by example as follows where all-parts are by weight.

EMM E in a rubber stock compounded as follows.

and polymethylene polyphenylisocyanate (PAPI) for NCO NCO where n has an average value of 1.2 and a Brookfield viscosity of 1,500 cps measured at 25 C. using a No. 3 spindle revolving at 250 rpm. The amounts of polyisocyanate and polycarbodiimide deposited on the cord is shown in Table l. The polyisocyanate treated cord is then dried to remove the solvent from the cord and the dried cord is then treated with an R/F/L/BNCO adhesive prepared as shown below by passing the cord through the adhesive at such a rate as to deposit on the surface of the cord between about 3 percent to about 10 percent adhesive solids and preferably 4 percent as was deposited in the experiments listed in Table I. This may be achieved by passing the cord through the adhesive composition at the rate of between about 20 yards to about 30 yards per minute and then drying the adhesive on the cord at a temperature of about 425 F. for about 2 /2 minutes. The treated cord is then imbedded lory tube fatigue test described in ASTM D88- 559T, Section 42, and also as described in US. Pat. No. 2,412,524. Table 1 shows how the conditions of cord treatment affect peel adhesion and fatigue. In each instant the same amount of second dip is applied to the cord, i.e., 4 parts per 100 parts of cord. Amounts between 5 and 25 parts may be used.

In the second dip containing a blocked isocyanate (BNCO) any of the polyisocyanates above listed may be blocked with an R/F resin in the following manner: 1 10 parts of resorcinol, 25 parts by volume of formalin (37 percent formaldehyde in methanol and water), and 20 parts by volume of water is reacted together in a reaction vessel equipped with both heating and cooling coils, a reflux condenser and a suitable agitator. The mixture is heated to a reflux temperature 100 C.) and allowed to remain at this temperature for 15 minutes, after which an additional parts by volume of formalin was added to the reaction mixture over a period of 10 minutes. After being refluxed for an additional 30 minutes, the resin formed in the reaction vessel was allowed to cool to room temperature. A thick, syrupy resin (for convenience referred to as Resin A) containing 60 percent solids, a viscosity of 750 cps. and a pH of 7 was obtained.

Twenty parts of the Resin A described above is reacted with 6 parts of polymethylene polyphenylisocyanate for 48 hours at 72 F. At the end of this time, the resulting reaction mixture is treated with 0.1 part of sodium hydroxide and 100 parts of water. The resulting neutralized resin blocked polyisocyanate maybe used Rubber Stock Parts by Weight May be Used In compounding the rubber stock in accordance with the formulation set forth above, a masterbatch of ingredients l and 2 are made with the carbon black and mixed on a mill to a temperature of about 1 10 C. and may be mixed at a temperature as high as 140 C. The resulting carbon black masterbatch is then cooled and the remaining compounds are mixed into the batch in the order indicated above to a temperature of about 70 C. and may be mixed at a temperature as high as 100 C.

The treated cord is then imbedded in this rubber and cured for l 1 minutes at 310 F. at psi. The cord peel force and fatigue are expressed on a rating of 100 for the control in which no polycarbodiimide is used in the first dip.

A heat durability (fatigue) test is made by forming a tube of rubber reinforced with the cord first treated with a polyisocyanate, then with the R/F/L/BNCO adhesive and then tested in accordancewith the Malas such or may be allowed to age for 8 hours before being used, (and for convenience to be referred to as resin BNCO).

The R/F/L/BNCO adhesive used as a second cord treatment is prepared as follows: a 20 percent solids This R/F/L adhesive is prepared by adding 98 parts made of such material as regenerated cellulose @1150 of the resorcinol to 196 parts of water, followed by the known as rayon, linear polyamides also known as nylon addition of 53 parts of formaldehyde. The resulting 6, nylon 66, and aromatic nylons such as pmixture is aged for 1 hour and then 1,152 parts of teraminobenzoic acid polymer (p-abap) as described in polymer rubber latex is added. The resulting mixture is 5 French Pat. No. 1,526,745, linear polyesters such as aged for a period of 72 hours. After aging, the balance polyethylene terephthalate also known as Dacron and of the water is added. To 65 parts of this R/F/L compo- Vycron, linear polyaminotriazoles, glass fibers, linear sition is added 35 parts of the resin blocked isocyanate polycarbonates, linear polyethers and polyurethanes, BNCO described above and allowed to age at 72 F. for and linear polyolefins. Especially improved adhesion 4 hours. This is the adhesive used for the second treatand resistance to fatigue is found when bonding the meat of the tire cord. polyesters and the polyamides to rubber. The tire cord The following table sets forth experiments all of treated by the process of this invention is made in a which were run in accordance with the procedure set conventional manner using, for example, polyethylene forth in Example 1. terephthalate filaments as a yarn having a total denier Table] Effect of First Dip Reaction Products On Cord Properties lst Dip 2nd Dip 1st Dip 1st Dip (Control) 1st Dip Pick Up (Control) (Filtered) PCD Pick Up R/F/L/BNCO PCD PAPI Peel Force 100 106 104 .02 .4 4. Fatigue 100 150 I40 .02 .4 4.

From the data shown in Table l, it isobserved that of approximately 7,800 drawn 6 to l to about 1,3 00 d ethe presence of the polycarbodiimide (PCD) is essennier which yarn is plied 8 turns per inch, 3 plies of tial in order to produce the effect obtained on the tire which are twisted 8 turns per inch inreverse direction cord fabric in regard to peel ,force and fatigue. The 1st to form a cord referred to as 1,300/3,8/8. dip control l contained 0.4 part of PAPI but no poly- The treatment of polyester fiber by the method of carbodiimide and was aged for 20 hours. This same 1st this invention is especially effective in the construction dip control was filtered and an improvement in peel of a conventional tubeless pneumatic tire comprising force and fatigue was observed at (2).The requirement an open-bellied, hollow annular body terminating in to mechanically filter the recycled solvent is an expenspaced apart bead portions as described in Us. Pat. sive operation and the present invention produced a No. 2,987,094. The tire is made with plies of polyester similar effect but without the added operation of filtracord bonded to rubber with the polyisocyanate pretion as shown at (3) where 0.02 part of PCD was added treatment followed by treatment with the R/F/L/BNCO to the 1st dip control. All cords treated as shown at l adhesive as described above as av second dip, dried on (2) and (3) also were treated with a second dip of the cord at about 425 F. for about 2 /2 minutes.

R/F/ /BNCO, dried and then imbedded in rubbe While certain representative embodiments and destock and tested to obtain the peel force and fatigue tails have been shown for the purpose of illustrating the data shown in Table l. invention, it will be apparent to those skilled in this art The effect Of the amount of polycarbodiimide added that various changes and modifications may be made to the polyisocyanate solvent first dip is shown in Table therei without departing from the spirit or scope of 11. the invention.

Table H What is claimed is:

l. A process for the treatment of atire cord fabric 0 Effect of Polycarhodiimide on the Fatigue 5 whlch complilses passmg the f b through at least n Durability of Dipped Polyester Cord solvent solution of an organic polyisocyanate contain- P a] Force Fan ue ing' from about 0.01 part to about 1.0 part by weight of e Polycarbodiimide PAP] Rating Rati ng polycarbodnmlde P 100 p hy weight q 2. A process wherein the fabric treated as in claim 1 (Castro!) g '33 2 is treated with a second dip containing rubber latex, a

1 t 83 217 resinous phenol/aldehyde reaction product and an or- 5g ganic polyisocyanate/water soluble thermoplastic resin 93 188 addition product, the resin in the addition product :30 .4 92 170 being the product of the reaction of an aldehyde with a phenol.

r r t 3. The process of claim 1 wherein the solvent is an The conditions set forth in Table I at (3) are repeated liphati chl ri ated hydrocarbon selected f h here but the amount of the polycarbodiimide use i group consisting of trichloroethylene, dichloroethan e, varied as shown. All parts are by weight per 100 parts .and trichloroethane. of solvent. 4. The process of claim 1 where the polycarbodii- The combination of the first and second cord-treatmide is present in an amount from about 0.02 to about ments of this invention may be applied to any tire cord 0.4 part per parts ofsolvent. tending to take up'moisture and includes those cords. 5. The process of claim 4 where the polyisocyanate is present in an amount from about 0.1 to about 2 parts 8. The process of claim 1 wherein the solvent is 1,1,1- per 100 parts of solvent. trichlorethane.

The Process of Clalm 1 Where!" the polylsocyanate 9. The article resulting from the process of claim 1.

is polymethylene polyphenylisocyanate.

7. The process of claim 1 wherein the polycarbodiimide has an n value of less than 10 in the general formula 10. A heat stable structure comprising rubber reinforced with the article of claim 9. 

2. A process wherein the fabric treated as in claim 1 is treated with a second dip containing rubber latex, a resinous phenol/aldehyde reaction product and an organic polyisocyanate/water soluble thermoplastic resin addition product, the resin in the addition product being the product of the reaction of an aldehyde with a phenol.
 3. The process of claim 1 wherein the solvent is an aliphatic chlorinated hydrocarbon selected from the group consisting of trichloroethylene, dichloroethane, and trichloroethane.
 4. The process of claim 1 where the polycarbodiimide is present in an amount from about 0.02 to about 0.4 part per 100 parts of solvent.
 5. The process of claim 4 where the polyisocyanate is present in an amount from about 0.1 to about 2 parts per 100 parts of solvent.
 6. The process of claim 1 wherein the polyisocyanate is polymethylene polyphenylisocyanate.
 7. The process of claim 1 wherein the polycarbodiimide has an n value of less than 10 in the general formula
 8. The process of claim 1 wherein the solvent is 1,1,1-trichlorethane.
 9. The article resulting from the process of claim
 1. 10. A heat stable structure comprising rubber reinforced with the article of claim
 9. 